I have to support what ecg_limey wrote...
It didn´t was a big differnce between A7 and irrlicht when I tried it, other than irrlicht having some usefull features missing and also having some bad design (at least that is what I would call irrlichts way to handle shaders and those strange animators).
I think that ecg_limey is mainly talking about rendering things like water, sky, shadows, plants, ...
For which the concepts are always the same one may prefer to use a plugin for some of those things to have it really advanced but there is no big difference it is just a fluent process where you get to know more and more new stuff but you don´t really notice it as the concepts are basicly always the same.